In the art of industrial chimney manufacture, the use of alloy materials to resist corrosion has become more acceptable in recent years, in spite of the relatively high costs associated with such materials.
For the past several years, electric utilities and other industries in the U.S. have been required by law to reduce the amount of sulfur dioxide and other recognized pollutants emitted by their activities. One method to capture sulfur dioxide is the use of wet lime or limestone scrubbers. However, the use of these systems produces a wider range of chimney operating conditions ranging from low temperature, highly acidic, to alkaline at high temperatures. Alloy materials such as alloy 625 and some stainless steels have been recognized as providing superior corrosion resistance to the broad spectrum of operation encountered downstream of FGD systems. However, the cost of alloy materials is prohibitive.
The present inventor is a joint inventor named in the U.S. patent of Parker et al 4,265,166, issued May 5, 1981, which patent relates to a chimney lining system which can utilize the superior corrosion resistance of alloy steels in scrubbed flue gas environment without using a heavy, very expensive alloy plate. The Parker et al system is particularly directed toward retrofit projects where the membrane would be installed within an existing steel lining. The system requires the use of flexible suspenders which permit radial expansion and uses horizontal corrugations for axial expansion. The resulting annulus between the membrane and the steel lining is subject to a partial vacuum pressure to enable the membrane to resist negative pressure and potential implosions within the chimney. Considered in the wider realm of industrial chimney manufacture, use and maintenance, the Parker et al system can be seen to possess certain disadvantages or shortcomings, including:
(a) The horizontal corrugation providing axial expansion protrudes into the gas stream and, as a consequence, is subject to erosion. PA1 (b) The use of a partial vacuum pressure to resist negative pressure and implosions facilitates entry of contaminants into the annulus which will accelerate corrosion if cracks or holes occur. The vacuum pressure may also require additional stiffening on the exterior of the existing lining. PA1 (c) Once installed, the membrane cannot be serviced or inspected since it is hidden by the presence of the existing steel liner. PA1 (d) The system is not readily adaptable to new construction.
In my aforementioned copending parent patent application I have disclosed a chimney lining system in which a membrane, typically 60 mils thick, of corrosion-resistant alloy material is suspended within an external skeletal framework of less-expensive carbon steel. Hangers provide for radial expansion of the liner. However, inward movement of the hangers is restrained. Axially spaced circumferential corrugations located midway axially between where two membrane sections are stiffened, joined and connected to the framework, provide for axial expansion. The external framework is disposed within a tubular concrete chimney column. At several levels, grillages support the external framework from the wall of the chimney column. The structural grillages may bear upon load cells equipped to signal the build-up of sludge on the interior of the liner.
The entire disclosure of the parent application is hereby incorporated herein.